Electric circuit interrupter



Aug. 3, 1937. H. BURMEISTER ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 28,1937 Inventor: Hermann Bun e'lste'r", y iVm z is Attor'neg.

Patented Aug. 3, 1937 ELECTRIC INTEBBUP'IEB Hermann Burmeiatcr,Berlin-Spandau, Germany, 'aseignor to General Electric Company, acorporation of New York Application January 28, 1937, Serial No. 122,773In Germany May 16, 1936 5 (Cl. 200l 44) This invention relates toelectric circuit interrupters of the air-break expulsion type wherein a'gas formed by decomposition of a material by the are upon opening ofthe circuit is utilized to interrupt the arc.

In a well-known form of circuit interrupter of the aforesaid type, thearc is drawn in a confining insulating structure, such as a tubecomposed of material which under the influence of the are heat emitsgases or vapors tendingto extinguish the arc. The interrupting capacityof a circuit breaker of this type wherein the gas forinterrupting thearc is released by the are heat from solid materials forming the wallsof the confining insulating structure, depends primarily on the rapiditywith which appreciable amounts of arc-extinguishing gas can be releasedunder the influence of the arc, particularly in the case of low currentinterruptions. The interrupting capacity also depends on thecharacteristics of the gas so formed. I In the latter case, it is knownthat carbonic acid has many advantages as an arc extinguishing medium.In practice, however, the use of carbonic acid has been limited becauseof the comparatively complicated and expensive switching installationsheretofore considered necessary.

" With reference to the rapidity of generation of the arc extinguishinggas in appreciable quantities under the influence of the are, fiber hasproved satisfactory. However, due to the hygroscopic characteristics ofthe fiber, this material has not stood up well in operation. An-

other known material for releasing gas by action of the arc is boricacid which contains chemically combined water. In the circuit openingprocess the water is released under infiuence of the arc and isevaporated to form an are extinguishing vapor. In this case, however,the evaporation is not free of residue so that the original propertiesof the wall surfaces adjacent the arc are not obtained after repeatedcircuit interruptions.

It has also beenproposed to make the arc-extinguishing tube of fibrousmaterial impregnated with a urea artificial resin. In this case, whereinmainly nitrogen acts as the arc extinguishing gas, the fibrous materialsor carriers must be so selected that they readily disintegrate to formgas underinfluence of the are without leaving undesirable residue assoot. Accordingly,the cost of the arc extinguishing material in thiscase is an important factor.

In accordance with the present invention the advantages inherent in theuse of carbonic acid as an arc extinguishing medium and in a materialcapable of releasing gas at a high rate for interrupting the are areobtained without disadvantageous results by the use of oxalic acid asthe gas emitting material. The oxalic acid may either contain water orbe free of water and may be used either with or without materials givingofi oxygen, such as organic peroxide or per-salts.

Under the influence of the arc, the oxalic acid disintegrates tocarbonic acid and water at a high rate. The caTbonic acid which issuitably utilized to interrupt the arc in a manner hereinafter describedis released immediately and in large quantities, while the solvent waterpresent evaporates without being essential to or materially influencingthe arc interruption. Since oxalic acid readily disintegrates upon theaddition of oxygen and by the addition of materials gas may beconsiderably increased.

or without the addition of a binding agent in powder form. As examplesof binding agents, inorganic agents, such as plaster of Paris, clay,etc. and organic agents such as highly oxidized oils, such as, forexample, linseed oil and wood oil, or prepolymerized artificial resin,as, for in- I stance, a. urea artificial resin may be used.

Referring more particularly to the drawing which illustrates a simpleform of circuit interrupter to which the present invention isapplicable, the single figure thereof is an elevational view partly insection of a circuit interrupter of the air-brake expulsion type.

In a structural embodiment of the invention it is preferable,particularly when the gas-emitting material for confining the arc is intubular shape, to provide a strong reinforcing tube therefor because ofthe stresses incident to circuit interruption.

As illustrated, a mechanically strong reinforcing tube I composed of asuitable fibrous material, for example, is provided with an inner liningat 2 composed of the oxalic acid gas-emitting material above described.The are which is formed upon opening of the circuit is drawn through thetubular structure by the movable rod contact 3 which coacts with thefixed contact 4 at the upper closed end of, the tubei The tube has asleeve fit with respect to the rod contact so that the arc is either inclose proximity to or What I claim as new and'desire secure by LettersPatent of the United States is: v

1. An electric circuit interrupter comprising 15 means for opening thecircuit so as to form an arc, and an insulating structure disposedadjacent and in confining relation to said arc, the walls of saidstructure in proximity to said arc being composed of oxalic acid.

20 2. An electric circuit interrupter comprising means for opening thecircuit so as to form an arc, and an insulating tubular structure withinwhich said are is drawn, said tubular structure being in confiningrelation to said are and consisting of a reini'orcing material having aninner lining composed chiefly oi. oxalic acid.

3. An electric circuit interrupter comprising means for opening thecircuit so as to form an arc, and an insulating structure disposedadjacent and in confining relation to said arc, the walls of saidstructure in proximity to said arc being composed of oxalic acid and aper-salt.

4. An electric circuit interrupter comprising means for opening thecircuit so as to form an arc, and an insulating structure disposedadjacent and in confining relation to said arc, the walls of saidstructure in proximity to said are being composed of oxalic acid, and abinding agent consisting of a highly oxidized oil.

5. An electric circuit interrupter comprising 'means for opening thecircuit so as to form an arc, and an insulating structure disposedadjacent and in confining relation to said arc, the walls of saidstructure in proximity to said arc being composed of oxalic acid, and abinding agent consisting of a prepolymerized artificial resin.

HERMANN BURMEIS'I'ER.

